Pool season · Montana
Missoula Pool Season: the Year on One Bar
Last updated: July 25, 2026 · dates · water temp
This is the one-page view of Missoula's pool year: both model windows, the estimated water-temperature curve, and today's live position on the season bar. The detailed checklists live on the opening and closing guides; this page is the calendar you check between them.
Missoula, MT — 57 swim days a yearEach dot on the bar is one week of Missoula's typical year, colored by what the model says that week is for: gray weeks are off-season, hollow teal marks the opening window (May 31–June 21), solid teal is swim season, and hollow amber is the closing window ending September 18. The black marker is today — its position against the colors is the entire executive summary.
The Missoula pool calendar
Opening — target June 7
Open by June 7 — a two-week head start on the June 21 crossing keeps startup chemistry small and beats the local service rush.
Closing — deadline September 18
The window opens September 8 once water leaves the algae zone; the model deadline is September 18, a week ahead of the October 1 freeze normal.
Estimated water temperature by month
This is Missoula's typical-year water curve: the same EWMA model as the live widget, run on the 1991–2020 normals instead of this week's weather.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 26° | 28° | 35° | 42° | 50° | 57° | 65° | 70° | 63° | 52° | 39° | 29° |
The curve peaks near 70°F — comfortable-water months here usually involve a heater or a solar cover.
Every station tells its own story: compare this curve with Billings's pool season or jump back to the Montana season index to see the statewide spread.
Missoula pool season FAQ
When should I open my pool in Missoula, MT?
Open by June 7 — the model places Missoula's 61°F crossing about two weeks later, and every warm day you wait pushes the water toward the 65°F algae zone. The Missoula opening guide has the 12-step sequence.
When should I close my pool in Missoula?
Close by September 18: cool water keeps its winter chemistry, but freeze damage is the hard stop. The Missoula closing guide sequences the work backward from that date.
How long is the swim season in Missoula?
Missoula averages 57 days a year with normal highs of 80°F or better — right on the statewide median. The Montana season index ranks all 2 covered cities by the same metric.
How warm does pool water get in Missoula?
An unheated pool near Missoula typically peaks around 70°F in high summer and bottoms out near 26°F in winter, never quite reaching the 78°F comfort line without a heater or solar cover. The month-by-month curve above shows the whole cycle; the methodology page explains the ±5°F error bars.
Email me when Missoula hits the closing window
Data: NOAA 1991–2020 climate normals via Missoula 2 NE (3.0 mi); live outlook by Open-Meteo. Attribution: sources · assumptions: methodology.